[sdiy] VCF caps in modern synths

cheater cheater cheater00social at gmail.com
Sun Mar 28 23:38:59 CEST 2021

On Sun, Mar 28, 2021 at 11:26 PM Neil Johnson <neil.johnson71 at gmail.com> wrote:
> Hi,
> Justin Herrmann wrote:
> > I think the https://passive-components.eu/dc-and-ac-bias-dependence-of-mlcc-capacitors-including-temperature-dependence/
> >
> > article is great, and I agree with its findings. It doesn't say anything about C0G though. It's about X5R and X7R.
> Actually it does.  First it correctly identifies C0G/NP0 as Class I dielectrics:
> "Dielectric materials for MLCCs come in three categories. Class I
> materials (for COG and NPO parts) are very stable, but can achieve
> only low εr"
> And then goes on to say that they don't bother testing Class I parts
> as they are known to be very stable:
> "It is still the common understanding that Class I ceramics have very
> little or no DC and AC bias dependence and therefore they were not
> included in the study."
> From the same website, a page on Class I ceramics:
> https://passive-components.eu/class-i-ceramic-dielectrics-types-performance-applications/
> None of the capacitor manufacturers bother with charts of DC bias
> effects on C0G/NP0 capacitors because (a) it would be a horizontal
> straight line, and (b) everyone knows that C0G/NP0 capacitors are very
> stable, that's why you choose them.  What you don't choose them for is
> high capacitance, because the dielectric is thicker and so the
> capacitance density is very low.  Fine up to a few tens on nF, but
> beyond that the prices start to get silly.
> Neil

Aye, right... so I guess that makes C0GNP0 non-starters for filters,
then? I think I've had this conversation 10 years ago... Glad to be
able to re-discover this amazing facet of electronics over and over!

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